This invention relates generally to a system for monitoring the frequency of a periodic function and indicating whether or not the function frequency differs from a given frequency and, more particularly, it relates to such a system for use in monitoring rotating shafts and the like in agricultural equipment.
In many types of machines, it is often necessary or desirable to monitor a condition or function and to provide for an indication or alarm whenever the frequency of the periodic function differs from a predetermined frequency. For example, in agricultural equipment such as combines, planters, or the like, it is important for the operator to know whenever the speed of a shaft is slower than its normal operating speed because such a slow-down often indicates that the machine is malfunctioning due to an overloaded auger, slipping belt, worn bearing, plugged straw walker chamber, or the like. Such malfunctions obviously can cause significant losses of time and money. Moreover, alerting the operator of the machine to a malfunction as soon as it occurs often enables the operator to correct the cause of the malfunction and thereby avoid the possibility of a much more serious malfunction such as the breakage of a part or burning out of a bearing, which would disable the machine for a relatively long period of time.
There are presently available on the market monitoring systems which very successfully perform such monitoring. One such monitoring system, for example, is disclosed in U.S. Pat. No. 3,739,367 to Fathauer, which is assigned to the assignee of the present invention. In certain monitoring applications, however, it would be desirable to have a system which is easily adaptable to simultaneously monitoring number of periodic functions and has a wide monitoring range at an economical cost.
It is therefore an object of the invention to provide a new, improved system for monitoring the frequency of a periodic function and indicating whether or not the frequency differs from a predetermined frequency.
It is a further object of the invention to provide such a system which monitors on a period-by-period basis.
It is another object of the invention to provide such a system which has a relatively wide monitoring range.
It is yet another object of the invention to provide such a system which is adaptable to simultaneously monitor a number of periodic functions.